共查询到20条相似文献,搜索用时 15 毫秒
1.
Inclusive jet differential cross sections for the reaction with quasi-real photons have been measured with the ZEUS detector at HERA. These cross sections are given for the photon-proton
centre-of-mass energy interval 134 277 GeV and jet pseudorapidity in the range in the laboratory frame. The results are presented for three cone radii in the plane, . Measurements of above various jet-transverse-energy thresholds up to 25 GeV and in three ranges of W are presented and compared to next-to-leading order (NLO) QCD calculations. For jets defined with differences between data and NLO calculations are seen at high and low . The measured cross sections for jets defined with are well described by the calculations in the entire measured range of and . The inclusive jet cross section for GeV is consistent with an approximately linear variation with the cone radius R in the range between 0.5 and 1.0, and with NLO calculations.
Received: 11 February 1998 / Published online: 2 July 1998 相似文献
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The H Collaboration 《The European Physical Journal C - Particles and Fields》2003,29(4):497-513
Inclusive jet cross sections are measured in photoproduction at HERA using the H1 detector. The data sample of
events in the kinematic range of photon virtualities
and photon-proton centre-of-mass energies
represents an integrated luminosity of
. Jets are defined using the inclusive
algorithm. Single- and multi-differential cross sections are measured as functions of jet transverse energy ET jet and pseudorapidity
in the domain
and
. The cross sections are found to be in good agreement with next-to-leading order perturbative QCD calculations corrected for fragmentation and underlying event effects. The cross section differential in ET jet, which varies by six orders of magnitude over the measured range, is compared with similar distributions from
colliders at equal and higher energies.Received: 24 February 2003, Revised: 26 May 2003, Published online: 11 July 2003 相似文献
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The ZEUS Collaboration J. Breitweg et al. 《The European Physical Journal C - Particles and Fields》1998,5(1):41-56
Differential dijet cross sections have been measured with the ZEUS detector for photoproduction events in which the hadronic
final state containing the jets is separated with respect to the outgoing proton direction by a large rapidity gap. The cross
section has been measured as a function of the fraction of the photon () and pomeron () momentum participating in the production of the dijet system. The observed dependence shows evidence for the presence of a resolved- as well as a direct-photon component. The measured cross section
increases as increases indicating that there is a sizeable contribution to dijet production from those events in which a large fraction
of the pomeron momentum participates in the hard scattering. These cross sections and the ZEUS measurements of the diffractive
structure function can be described by calculations based on parton densities in the pomeron which evolve according to the
QCD evolution equations and include a substantial hard momentum component of gluons in the pomeron.
Received: 20 April 1998 / Published online: 2 July 1998 相似文献
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The H Collaboration C.?Adloff et al. 《The European Physical Journal C - Particles and Fields》2002,25(1):13-23
Dijet cross sections as functions of several jet observables are measured in photoproduction using the H1 detector at HERA.
The data sample comprises data with an integrated luminosity of 34.9 pb. Jets are selected using the inclusive algorithm with a minimum transverse energy of 25 GeV for the leading jet. The phase space covers longitudinal proton momentum
fraction and photon longitudinal momentum fraction in the ranges and . The predictions of next-to-leading order perturbative QCD, including recent photon and proton parton densities, are found
to be compatible with the data in a wide kinematical range.
Received: 4 January 2002 / Published online: 12 July 2002 相似文献
7.
The H Collaboration 《The European Physical Journal C - Particles and Fields》2005,38(4):437-445
Results are presented on the photoproduction of isolated prompt photons, inclusively and associated with jets, in the
center of mass energy range 142 < W < 266 GeV. The cross sections are measured for the transverse momentum range of the photons
GeV and for associated jets with E
T
jet > 4.5 GeV. They are measured differentially as a function of
, the pseudorapidities
and
and estimators of the momentum fractions
and x
p
of the incident photon and proton carried by the constituents participating in the hard process. In order to further investigate the underlying dynamics, the angular correlation between the prompt photon and the jet in the transverse plane is studied. Predictions by perturbative QCD calculations in next to leading order are about
below the inclusive prompt photon data after corrections for hadronisation and multiple interactions, but are in reasonable agreement with the results for prompt photons associated with jets. Comparisons with the predictions of the event generators PYTHIA and HERWIG are also presented.Received: 13 July 2004, Revised: 15 November 2004, Published online: 17 December 2004 相似文献
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I. A. Korzhavina 《Physics of Atomic Nuclei》2002,65(2):249-254
The first measurement of the cross sections for D*±-meson diffractive photoproduction was performed with the ZEUS detector at the HERA ep collider by using an integrated luminosity of 38 pb?1. The measurement was performed for photon-proton c.m. energies in the range 130<W<280 GeV and photon virtualities in the region Q 2<1 GeV2. The product D*± mesons were reconstructed for p T D* >2 GeV and ?1.5<η D*<1.5 from the decay channel D*+ → D 0 π s + with D 0 → K ? π + (+ c.c.). The diffractive component was selected for 0.001 <x P<0.018. The measured cross section in this kinematical range is $\sigma _{ep \to e'D^ * X_{p'} }^{diff} = 0.74 \pm 0.21(stat.)_{ - 0.18}^{ + 0.27} (syst.) \pm 0.16(p.diss.)$ nb (ZEUS preliminary). The measured integrated and differential cross sections are compared with theoretical expectations. 相似文献
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《Nuclear Physics B》2004,700(1-3):3-50
Jet substructure and differential cross sections for jets produced in the photoproduction and deep inelastic ep scattering regimes have been measured with the ZEUS detector at HERA using an integrated luminosity of 82.2 pb−1. The substructure of jets has been studied in terms of the jet shape and subjet multiplicity for jets with transverse energies . The data are well described by the QCD calculations. The jet shape and subjet multiplicity are used to tag gluon- and quark-initiated jets. Jet cross sections as functions of , jet pseudorapidity, the jet–jet scattering angle, dijet invariant mass and the fraction of the photon energy carried by the dijet system are presented for gluon- and quark-tagged jets. The data exhibit the behaviour expected from the underlying parton dynamics. A value of αs(MZ) of was extracted from the measurements of jet shapes in deep inelastic scattering. 相似文献
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We present results for next-to-leading order calculations of single jet inclusive cross sections by resolved photons inep-collisions at HERA. The dependence on the jet recombination cut and on the choice of the renormalization and factorization scales is studied in detail. 相似文献
12.
《The European Physical Journal C - Particles and Fields》2006,47(3):597-610
A measurement of charm and beauty dijet photoproduction cross sections at the ep collider HERA is presented. Events are selected
with two or more jets of transverse momentum pt
jet1(2)>11(8) GeV in the central range of pseudo-rapidity -0.9<ηjet1(2)<1.3. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter,
in the transverse plane, of tracks to the primary vertex, as measured by the H1 central vertex detector. Differential dijet
cross sections for charm and beauty, and their relative contributions to the flavour inclusive dijet photoproduction cross
section, are measured as a function of the transverse momentum of the leading jet, the average pseudo-rapidity of the two
jets and the observable xγ
obs. Taking into account the theoretical uncertainties, the charm cross sections are consistent with a QCD calculation in next-to-leading
order, while the predicted cross sections for beauty production are somewhat lower than the measurement. 相似文献
13.
Inclusive photoproduction of mesons has been measured for photon-proton centre-of-mass energies in the range GeV and photon virtuality 1 GeV. The data sample used corresponds to an integrated luminosity of 37 pb. Total and differential cross sections as functions of the transverse momentum and pseudorapidity are presented in restricted kinematical regions and the data are compared with next-to-leading
order (NLO) perturbative QCD calculations using the “massive charm” and “massless charm” schemes. The measured cross sections
are generally above the NLO calculations, in particular in the forward (proton) direction. The large data sample also allows
the study of dijet production associated with charm. A significant resolved as well as a direct photon component contribute
to the cross section. Leading order QCD Monte Carlo calculations indicate that the resolved contribution arises from a significant
charm component in the photon. A massive charm NLO parton level calculation yields lower cross sections compared to the measured
results in a kinematic region where the resolved photon contribution is significant.
Received: 9 July 1998 / Published online: 22 October 1998 相似文献
14.
J. J. Engelen S. J. de Jong M. Poletiek J. A. M. Vermaseren 《Zeitschrift fur Physik C Particles and Fields》1988,41(1):173-177
We present cross sections for heavy flavour production through photon gluon fusion in electron proton collisions at HERA energy. The electron photon vertex is taken into account explicitly, and theQ 2 of the exchanged photon ranges from nearly zero (almost real photon) to the kinematically allowed maximum. In our approach the scale is set by the mass of the produced quarks. Our formalism is also applicable to the production of light quarks as long as the invariant mass of the pair is sufficiently high, so we also give cross sections for \(u\bar u,d\bar d\) and \(s\bar s\) production. 相似文献
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J. M. Butterworth J. R. Forshaw M. H. Seymour 《Zeitschrift fur Physik C Particles and Fields》1996,72(4):637-646
The high energy photoproduction of jets is being observed at theep collider, HERA. It may be that the HERA centre-of-mass energy is sufficiently large that the production of more than one pair of jets perep collision becomes possible, owing to the large number density of the probed gluons. We construct a Monte Carlo model of such multiparton interactions and study their effects on a wide range of physical observables. The conclusion is that multiple interactions could have very significant effects upon the photoproduction final state and that this would for example make extractions of the gluon density in the photon rather difficult. Total rates for the production of many (i.e.≥3) jets could provide direct evidence for the presence of multiple interactions, although parton showering and hadronization significantly affect low transverse energy jets. 相似文献
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《The European Physical Journal C - Particles and Fields》2007,50(2):251-267
Differential photoproduction cross sections are measured for events containing D*± mesons. The data were taken with the H1 detector at the ep collider HERA and correspond to an integrated luminosity of 51.1 pb-1. The kinematic region covers small photon virtualities Q2 < 0.01 GeV2 and photon–proton centre-of-mass energies of 171 < Wγ p < 256 GeV. The details of the heavy quark production process are further investigated in events with one or two jets in addition
to the D*± meson. Differential cross sections for D*+jet production are determined and the correlations between the D*± meson and the jet(s) are studied. The results are compared with perturbative QCD predictions applying collinear- or kt-factorisation. 相似文献
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《Nuclear Physics B》1996,474(1):183-213
We treat hadron-hadron collisions where the final state is kinematically of the kind associated with double-pomeron-exchange (DPE) and has large transverse momentum jets. We show that in addition to the conventional factorized (FDPE) contribution, there is a nonfactorized (NDPE) contribution which has no pomeron beam jet. Within a simple model we compute DPE-two-jet total and differential cross sections at Tevatron energy scales, and show that the NDPE contribution is dominant. 相似文献